1. Field of the Invention
The present invention relates to a voltage detecting circuit, and more particularly to a voltage detecting circuit for detecting when voltage from a power supply falls outside of predetermined parameters.
2. General Background
With the increasing development of technology, computers have become essential electrical appliances in our lives. In addition, reliable and stable power supplies are essential to the computers.
To ensure quality performance of computers, testing the stability of power supplies in providing direct current (DC) voltages to a motherboard is needed in the manufacturing process. Each voltage requirement of the motherboard must be fulfilled within a determined range or tolerance. For example, if a 5V voltage is needed for providing power to a USB interface, the specifications may require that the voltage supplied be between 4.75V and 5.25V.
A typical voltage detecting circuit for testing voltages output by a power supply includes a voltage comparator for comparing the output of the power supply with a reference voltage, and a light emitting diode (LED) for indicating when the output voltage is not to specification.
However, the typical voltage detecting circuit does not indicate if the output voltage is greater than or lower than a specified range. In addition, the LED emits light only at the moment the abnormal voltage occurs and goes out when the voltage returns to the normal state. Therefore, an operator may overlook the transient occurrence and may not realize there is a fault needed to investigate.
What is needed is a voltage detecting circuit for detecting when voltage of a DC power supply is outside of specifications and alerting an operator to that fact even when it is a temporary or short term occurrence.